It is well known to supply donor mediums and receiver mediums used in printers in the form continuous webs that are wound onto a core until used. This method of web medium storage is highly efficient allowing a large amount of web medium to be supplied to a printer in a form that is easy to manufacture and readily accessible for use during printing. Accordingly, printers are often designed with medium supplies that use core wound webs of medium.
Typically, the large amount of web medium that can be stored on a core has a high mass. This in turn requires that the core has a beam strength that is sufficient to support the mass of web medium when loaded in the printer and a yield strength along an axis of rotation that is sufficient to transfer any forces required to control rotation of the core and associated web medium. For these reasons the core itself can have a relatively high mass and thus the overall mass of a core and associated web can be significant.
The high mass of a core and associated web medium increases demands made upon the printer in applying forces to control rotation of the core and associated web. Specifically, it will be appreciated that controlled supply of a web medium from a core requires an ability to precisely accelerate and decelerate the core and associated web. The mass of the core and associated web creates significant inertial loads that must be overcome by the forces that create such acceleration and deceleration. Such inertial loads can be particularly high where the core and associated web medium are used in printers that draw web medium from the core at rates that compel high speed rotation of the core.
Accordingly, an interface between the core and a mounting that is rotated to apply forces to drive the core and associated mounting must be engaged to the core in a manner that is secure enough to keep the core from slipping relative to the mounting when such forces are applied. In some printers, the core and core mounting that drives the core will have mechanical features such as notches or grooves that extend longitudinally along the length of the core that can engage with protrusions provided by the mountings. These approaches help to provide such a secure engagement. One example of this is shown in U.S. Pat. No. 6,425,548, issued to Christensen et al. on Jul. 30, 2002 in which a core and hub assembly are provided for a printing device. This device provides keys that are mounted at a proximal end of a mount which serve to transmit torque when engaged with a co-designed core. It will be appreciated that this system requires the use of a complex core and a complex mounting.
What is also needed therefore are printers and web medium supplies for use in printers that can reliably apply forces that drive the core and web against a high inertial load, yet do not increase the complexity of core, mounting or the process of loading a core in a printer web medium supply.
It is also desirable to provide a designer of a printer with greater design freedom with respect to the size, weight complexity and expense of the core and associated web and to further have greater design freedom with respect to the size, weight, cost and performance capability of the printer. However, the mass of the core and associated web can reduce such freedom. Thus, what are also needed are web medium supplies and methods that allow greater design freedom despite the high mass and high inertial loads provided by the core and associated web.
It is also well known that each web medium used by a printer has characteristics that can influence the appearance of a print made using the web medium. Many existing reader systems are known that read markings on a core or that detect the presence of a radio frequency identification tag to allow automatic determination of data from which the characteristics of such a web can be determined. However, reader systems can be complex and expensive. Alternatively, less complex mechanical encodements such as notches in a core can be detected using less complex readers. However such encodements are vulnerable to damage. Thus what is also needed in the art are web medium supplies and methods that can automatically determine data regarding a web that is on a core using a less complex, less expensive, and more robust approach.
Further, it will be appreciated that as the mass of a core and associated web increases the demands made on an operator in mounting the core and associated web in a printer also increase. As an initial matter the high mass of the core and associated web can be difficult to lift. Further, the high mass of the core and associated web can make it difficult for an operator to adjust a velocity of the core and associated web as is required to position the core and associated web during loading. This is because the inertia of the core and associated web is high and therefore any attempt to accelerate or decelerate a core and associated web must be made against an inertial load. These difficulties can cause a user to drop or otherwise mis-handle a core when loading the core into a printer which can damage the core, the web medium or the printer.
In some instances, the process of loading a core and associated web into a printer is further complicated because the proper orientation of a core within a pair of mountings that hold the core for rotation in a printer may not be apparent. Mis-assembly of the core to mountings that hold the core for rotation can interrupt or undermine the printing process for example, by causing images to be printed on the wrong side of a receiver medium.
What is further needed therefore are web medium supplies and methods that reduces the risk that a core and associated web will be mis-loaded or mis-assembled without making loading more difficult.